Gastric cancer is the second most common cause of cancer-related death world-wide, with the 5-year survival rate less than 15%. The high mortality rate is due to delayed diagnosis as early stages of gastric cancer (such as dysplasia and early adenocarcinoma) are usually asymptomatic. Early diagnosis and surgical intervention of gastric cancer is crucial to a better prognosis, which increases the 5-year survival rate to 50%. Currently, strointestinal endoscopy is the gold standard of diagnosis. However, this is an uncomfortable procedure with its own risk and the operation is not suitable for large-scale screening. However, sensitive and specific non-invasive test for diagnosis of gastric cancer is not currently available. There is a real need to identify reliable serum protein biomarkers that are indicative of the presence of early gastric cancer for diagnostic purposes.
In the post-genomic era, it is realized that proteins are the work-horses of the body. Different metabolic pathways are manifested by proteins. Therefore, unique and specific proteins expressed in early stages of gastric cancer can be used as biomarkers. Pathologically, the progression of cancer is mainly manifested as uncontrolled growth in cancerous tissues, construction of new blood vessels and invasion into adjacent tissues. These changes will bring about concomitant changes in expression of proteins, including their formation, concentrations and interactions with other molecules. Through perfusion into tissues and organs by blood and lymph, proteins and the fragments from the cancer tissue enter the circulation. Defense response to the cancer by the body also produces another set of proteins. Hence, serum/plasma samples from clients will provide an ideal sample for screening of the occurrence of gastric cancer.